Depending on how close the modifier (beauty dish) is from the subject is what really makes the difference. In the sense of shooting head shots for hair and make-up ads a beauty dish is used in pretty close proximity. Usually you try to have a modifier slight larger than the subject within respect of distance. Like a 22" is popular for headshots because at two to three feet away it is a pretty good ration of size of subject to light source. This is where the characteristics or lack there of will shine through. If you back way off you essential start to use it like a large reflector, the light flattens out the shadows get defined and won't really notice the distinction. Just like a the inverse square rule, if you multiply the distance between light and subject by 2 you have to increase the power by 4, you can have a large light source but as you move it farther a away, it is smaller in relation to the subject. Like the sun is really the largest light source, but because it is so far away it is actually a very bright and tiny light source there for the light it cast is flat and the shadows are very hard edged and defined. The finish can affect white balance but is more for a desired specular quality. Silver will be more specular while white is less specular and is more flattering for less than perfect skin.